Parry’s good-luck story replicates that of an actor in the 1980s – in the same musical – also at the Theatre Royal Drury Lane. One night, during the show’s original run, the actor playing the other female lead, Peggy Sawyer, was taken ill shortly before the curtain went up with her understudy also unable to perform.

Mirroring the show itself, and faced with the performance being cancelled, a young actor in the ensemble said she knew the role and could do it. With little rehearsal she went on, and its producers anxiously rushed down to the theatre.

They watched an actor called Catherine Zeta-Jones go out and storm the stage. That break led on to her taking over the role full-time and catching the attention of TV and film producers as a result.

In fact, theatre has many stories like that of Parry’s, and even of actors being in two shows at the same time, but many never make the headlines. One of the greatest of these is Broadway legend Elaine Stritch who, in her seminal one-woman show, talked about being in two different productions at the same time but also in two different cities!

It was the work of Mamma Mia!’s canny press rep who ensured Parry’s appearance garnered some superb press coverage. Today, the show is a brand in itself, with less pressure on its management if they want to make an event of an understudy stealing the spotlight.

In fact, Parry’s appearance and subsequent promotion in 42nd Street proved very useful in putting both these established musicals back in the headlines. Her lucky break is similar to that of Natasha J Barnes, who was Sheridan Smith’s understudy on Funny Girl and stepped into a performance with little notice.

These opportunities may have come from someone else’s bad luck, but after that it’s all down to the replacement’s driving hunger, determination and confidence to succeed.

However, it’s also dependent upon the good fortune of being in a show where the producer takes the decision that releasing a news story about the understudy going on is an asset to the production.

Funny Girl’s producers faced a major problem when it became evident Smith’s departure was going to become an extended absence. With many tickets sold on her name, they mitigated this by turning Barnes into a ‘star is born’ news story that made audiences want to come and discover her for themselves. Barnes went on to become a leading lady in her own right.

A star’s absence is every producer’s nightmare. However, in some respects, and as Funny Girl demonstrated, a prolonged absence of a star may actually give the producer a better position to resolve a complex and potentially devastating production problem, compared to a star who is off with intermittent regularity.

This was a problem on the West End musical The Bodyguard where its star, Heather Headley, due to ill health, frequently missed performances. It took me three attempts to see her perform the lead role. On one of these occasions, she started the show and had to stop a short way into it.

The show’s second cover, Janet Kumar, was pushed on, stepping in mid-performance and she was terrific, but she didn’t get the same press coverage as Parry. For a new show in the West End – with reviews raving over Headley’s performance – news stories about the star regularly being off would have proved detrimental to the advance box office.

It’s also all about the timing that the understudy has to go on. In previews, a headline star being off can cause media speculation over the reasons why, which can be damning.

It’s naturally disappointing not to see the star perform but an understudy’s appearance can also be incredibly exciting to watch

In 2001, a preview of My Fair Lady at the National Theatre saw its lead, Martine McCutcheon, unable to play a performance at short notice. Following an announcement by director Trevor Nunn, understudy Alexandra Jay went on without any rehearsal. I happened to be in the audience and Jay was every bit the star, although sadly I doubt few people remember her name.

It’s naturally disappointing not to see the star perform but an understudy’s appearance can also be incredibly exciting to watch, especially if it’s their first appearance in the part. You watch it knowing that pure adrenaline is pumping through both the understudy and their nervous cast members alike.

However, I am amazed at how often the director or producer themselves do not audition the understudies. They are your disaster insurance on a production and arguably among the most essential people engaged.

Many will never get the lucky break Parry did, neither will we read about them going on, but tonight in theatres around the world, understudies will be waiting in their dressing rooms ready (if needed) to ensure the show must go on.

Parry’s recent appearance serves to remind us of the trust we place in them, and why their often thankless work on a production should be both better respected and highly valued.

We need your help…

When you subscribe to The Stage, you’re investing in our journalism. And our journalism is invested in supporting theatre and the performing arts.

The Stage is a family business, operated by the same family since we were founded in 1880. We do not receive government funding. We are not owned by a large corporation. Our editorial is not dictated by ticket sales.

We are fully independent, but this means we rely on revenue from readers to survive.

Help us continue to report on great work across the UK, champion new talent and keep up our investigative journalism that holds the powerful to account. Your subscription helps ensure our journalism can continue.